Lighting assembly

ABSTRACT

The light fixture includes a frame, an optically transmissive panel assembly, a set of light emitting diodes (LEDs), and driving circuitry. The frame has a frame length measured along a length axis and a frame width measured along a width axis, wherein the frame length is greater than the frame width. The optically transmissive panel assembly receives light from the set of light emitting diodes (LEDs) and emits light from an emission area in a patterned luminous intensity, using patterning optics adjacent a light guide plate. The driving circuitry is disposed within the frame and is operatively coupled to the set of LEDs and to a power supply external to the light fixture. The driving circuitry may include a first circuitry segment disposed within a first edge channel of the frame, and a second circuitry segment disposed within a second edge channel of the frame.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of U.S. Provisional Application No. 61/812,973 filed Apr. 17, 2013, entitled LIGHTING ASSEMBLY, the entire content of which is hereby incorporated by reference.

INCORPORATION BY REFERENCE

The present application incorporates by reference the following patent applications in their entireties:

U.S. Pat. Pub. No. 20130044512, entitled “FLAT PANEL LIGHTING DEVICE AND RETROFIT KIT,” published Feb. 21, 2013 (Ser. No. 13/473,918, filed May 17, 2012); and, U.S. Pat. Pub. No. 2012032062, entitled “FLAT PANEL LIGHTING DEVICE AND DRIVING CIRCUITRY,” published Dec. 20, 2012 (Ser. No. 13/473,929, filed May 17, 2012).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally solid state lighting, such as light emitting diode (LED) lighting, and more particularly to a LED luminaire.

2. Description of the Related Art

LEDs provide several advantages over conventional lighting sources, such as reduced power consumption, higher efficiency, longer life, and enhanced aesthetics. But unlike conventional omnidirectional incandescent, metal halide, sodium, or fluorescent lights, LEDs are directional in nature and require optics specifically configured to optimize the spread of light over a given area in order to meet the light output patterns necessary for many applications, such as under-cabinet lighting.

Under-cabinet lighting is typically added under a cabinet, shelf, or similar surface in order to produce localized lighting on a work surface. Under-cabinet lighting is often added to kitchen and pantry cabinets to provide task lighting on the countertops that is complementary to the general lighting of the room. The underside of cabinets provides an ideal location for task lighting because the light source is near the task and can be easily concealed to avoid glare. Under-cabinet lighting also can reduce shadows cast by the cabinets from the overhead lighting.

As will be disclosed below, the LED under cabinet light fixtures can serve as an efficient alternative to fluorescent and incandescent under cabinet lights that are well known in the prior art. LED under cabinet light fixtures require special optical design to avoid glare, bright spots, and provide enhanced uniformity of illuminance along the length and width of a countertop.

SUMMARY OF THE INVENTION

In one aspect, the light fixture of the present invention includes a frame; an optically transmissive panel assembly; a set of light emitting diodes (LEDs); and driving circuitry. The frame has a frame length measured along a length axis and a frame width measured along a width axis. The frame length is greater than the frame width. The optically transmissive panel assembly is disposed within the frame. The set of light emitting diodes (LEDs) extends along the length axis adjacent an edge surface of the optically transmissive panel assembly. The driving circuitry is disposed within the frame and operatively coupled to the set of LEDs. The driving circuitry is operatively coupled to a power supply external to the light fixture to power the set of light emitting diodes (LEDs). The optically transmissive panel assembly receives light from the set of light emitting diodes (LEDs) and emits light in a patterned luminous intensity distribution.

In a preferred embodiment, optically transmissive panel assembly includes a light guide plate. A patterning optics is adjacent the light guide plate. The patterning optics may be formed, for example, of a micro-prism film or sheet, or a micro-lens film or sheet.

In another embodiment, the optically transmissive panel assembly emits light in an asymmetric light distribution. The asymmetric light distribution may provide maximum luminosity in a transverse direction from the light fixture.

In yet another embodiment, the optically transmissive panel assembly emits light in a light distribution with narrowed beam angle.

In a further embodiment, for illuminating an elongate surface, the optically transmissive panel assembly has a diffusion angle for light emitted in a longitudinal direction, which is different than a diffusion angle for light emitted in a transverse direction. In one application of that embodiment, an array of light fixtures comprise downlights for illuminating the elongated surface below the light fixtures, the light fixtures being oriented with the length axis of each light fixture substantially parallel to a long axis of the elongated surface .

In a further embodiment, the light fixture is located adjacent an edge of an object, and the optically transmissive panel assembly emits light with maximum luminous intensity at an angle toward a location in front of the object.

In another broad aspect, the light fixture of the present invention includes a frame; a set of light emitting diodes (LEDs) within the frame; and, driving circuitry. The frame includes a first edge wall and a second edge wall. A first edge channel is defined within said frame adjacent said first edge wall, and a second edge channel is defined within said frame adjacent said second edge wall. Driving circuitry is disposed within said first edge channel and is operatively coupled to the set of LEDs, the driving circuitry being operatively coupled to a power supply external to the light fixture to power the set of light emitting diodes (LEDs). The driving circuitry comprises a first circuitry segment disposed within the first edge channel, and a second circuitry segment disposed within the second edge channel and in electrical communication with the first circuitry segment.

In one embodiment, the first circuitry segment and the second circuitry segment each comprise a printed circuit board, with components arrayed serially along the length of the printed circuit board. The first circuitry segment may be oriented vertically within the first edge channel. The first circuitry segment may be mounted to the first edge wall with a heat dissipating layer between the printed circuit board and first edge wall.

In another embodiment, the frame includes a third edge wall, and a third edge channel is defined adjacent to the third edge wall. The driving circuitry further includes a third circuitry segment disposed within the third edge channel and in electrical communication with the second circuitry segment.

These and further features of the disclosed technology will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the invention may be employed, but it is understood that the invention is not limited correspondingly in scope. Rather, the invention includes all changes, modifications and equivalents coming within the spirit and terms of the claims appended thereto.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Likewise, elements and features depicted in one drawing may be combined with elements and features depicted in additional drawings. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a perspective illustration of an embodiment of the light fixture of the present invention.

FIG. 2 is an exploded perspective view of the light fixture of FIG. 1.

FIG. 3 is a perspective illustration of the light fixture of FIG. 1, shown cutaway to reveal certain components thereof.

FIG. 4 is a cross-sectional view of the light fixture, taken along line 4-4 of FIG. 1.

FIG. 5 is a diagrammatic illustration of a light fixture in accordance with one aspect of the disclosed technology in which three edge channels are utilized.

FIG. 6 is a diagrammatic illustration of a light fixture in accordance with one aspect of the disclosed technology in which four edge channels are utilized.

FIG. 7 is a cross-sectional view of a portion of an embodiment of the light fixture, emphasizing the components of the optically transmissive panel assembly.

FIG. 8 is a perspective view showing application of the light fixtures of the present invention in an under cabinet environment.

FIG. 9 is a perspective view showing application of the light fixtures of the present invention in a vanity mirror environment.

FIG. 10 is a diagrammatic illustration of a LED array in accordance with one aspect of the disclosed technology.

FIG. 11 is a perspective view, partially cutaway of a portion of an embodiment of the light fixture of the present invention in which circuit components are arrayed along the length of the circuit board substrates, in order to reduce width of the circuit board substrates.

FIG. 12 is a schematic view showing application of the light fixtures of the present invention in a wall wash lighting environment.

FIG. 13 is a schematic view showing application of the light fixtures of the present invention in a step lighting environment.

FIG. 14 is a polar graph of candela distribution for an embodiment of the light fixture of the present invention providing an asymmetric light distribution.

FIG. 15 is a polar graph of candela distribution for an embodiment of the light fixture of the present invention providing a 25° narrow light distribution.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and the characters of reference marked thereon, FIGS. 1-4 illustrate an exemplary embodiment of the light fixture of the present invention, designated generally as 10. As can be easily seen in FIG. 1, the light fixture 10 includes a frame 12 having a frame length measured along a length axis 14 and a frame width measured along a width axis 16. The frame 12 provides structural support for the various components of the light fixture 10. The frame length is greater than the frame width.

Light is emitted from an emission area 18 at a front surface of the light fixture 10. The emission area 18 has a substantially rectangular aperture; wherein “aperture” indicates linear dimension(s) of the emission area including a first dimension along the length axis (i.e. aperture length) and a second, shorter dimension along the width axis (i.e. aperture width). Light emitted from emission area 18 may travel along a normal 64 to the emission area, or may travel in an off-normal direction. Axes A and B, directed away from the long edges of the light fixture 10, are parallel to the width axis 16. Axes C and D, directed away from the short edges of the light fixture 10, are parallel to the length axis 16. As used in this patent application, a “transverse direction” indicates a direction that deviates from normal 64 in a direction that is out of the plane that includes the normal 64 and at least one of the axes C and D; for example, directions A and B. As used in this patent application, a “longitudinal direction” indicates a direction that deviates from normal 64 in a direction that is out of the plane including the normal 64 and at least one of the axes A and B; for example, directions C and D. It should be noted than a transverse direction or a longitudinal direction need not be perpendicular from normal 64 but may be at an acute angle from the normal 64, and that emitted light may travel along an axis that deviates from normal 64 in both a transverse direction and longitudinal direction.

Exterior features of the frame 12 include a bezel portion 20 of the frame surrounding the emission area 18. As described herein, the bezel 20 may serve as a cover structure for interior components of light fixture 10. The front surface of the frame 12 may include a switch 22. Additionally, appropriate openings 24 and/or other cutaways may be provided for access by wires or other electrical connectors, such as wiring carrying AC power in, wiring carrying DC power in, and/or wiring carrying DC power out.

Referring to FIGS. 2-4, the frame 12 includes a first edge wall 28 and a second edge wall 30, each extending along the length axis 14. A first edge channel 32 is defined within the frame 12 adjacent the first edge wall 28. The first edge channel 32 is between the first edge wall 28 and a first inner wall 34. The first edge channel 32 preferably has a width of 18 mm or less, in some embodiments 15 mm or less, and in certain (most compact) embodiments 12 mm or less.

As described herein the driving circuitry 50, shown in highly schematic form in FIG. 2, may have a compact configuration compatible with narrow widths of first edge channel 32 as described above. For example, driving circuitry may have dimensions of approximately 20 centimeters in length, approximately 15 millimeters of width, and approximately 15 millimeters in height. In a preferred embodiment, the driving circuitry has an elongate aspect ratio, with a ratio of the length of the driving circuitry to the width of the driving circuitry (i.e. length-to-width ratio) of at least ten to one. It will be appreciated that the disclosed technology is not limited to these exemplary dimensions. The first edge channel 32 can take on other dimensions without departing from the scope of the disclosed technology. Such compact driving circuitry 50 can be obtained by employing miniaturized power and/or control boards. Additional techniques for miniaturized driving circuitry are disclosed below.

An optically transmissive panel assembly, designated generally as 26, is disposed within the frame 12. A set of light emitting diodes (LEDs) 36 is disposed within the frame and extends along the length axis 14 in proximity to the second edge wall 30 and adjacent an edge surface 38 (see also FIG. 7) of the optically transmissive panel assembly 26. The optically transmissive panel assembly 26 receives light from the set of LEDs 36 and emits light from the emission area 18.

The LEDs 36 may be supported as part of an LED panel structure, designated generally as 40, such as one or more array, strip, or bar of LEDs 36. Various forms of LEDs packaging may be employed, including for example surface mounted packages that mount LEDs to a printed circuit board. Surface mounting of LEDs typically dissipates heat efficiently. However, it is understood that other LEDs packaging such as pin mounted LEDs, and Chip-on-Board (COB) LEDs, may be utilized. As seen in FIG. 7, a lens 92 or other suitable structure may provide an optical interface between the LEDs 36 and a light guide plate 27 included in optically transmissive panel assembly 26. As used in the present patent application, the term “set of light emitting diodes” (or “LEDs”) optionally includes a lens or other optical interface between the LEDs and the optically transmissive panel assembly 26.

In the embodiment shown, the optically transmissive panel assembly 26 is substantially flat. The term “substantially flat optically transmissive panel assembly” as used in connection with the description of the various embodiments, is meant to include optically transmissive panel assemblies having a thickness that is substantially less than the length and width of the optically transmissive panel assembly. As discussed above, the length of the light fixture 10 is greater than its width, and likewise the substantially flat optically transmissive panel assembly has a length greater than its width. Advantageously, light fixture 10 has a substantially flat configuration, but may be of slightly non-uniform thickness due to the configuration of the optically transmissive panel assembly 26 or of another part of the light fixture 10 such as frame 12.

The term “optically transmissive panel assembly” encompasses all light-transmissive, reflective, or refractive structures in the light path from the set of light emitting diodes (LEDs)—but not including these LEDs or any lens or other optical interface adjacent the LEDs—to the emission area 18 (see e.g. the structures shown at 26 in FIG. 7). In one embodiment, the optically transmissive panel assembly includes a light guide plate 27 (LGP) in combination with light-reflective and light-transmissive films, sheeting, or coatings. The optically transmissive panel may include separate component parts assembled during production of light fixture 10, or may comprise a composite structure. In the embodiment of FIG. 2, optically transmissive panel assembly 26 includes light guide plate (LGP) 27, reflective film 44, patterning optics film 29 adjacent a surface of the light guide plate 27 opposite reflective film 44, and diffuser 42 at the front surface (emission area 18) of the optically transmissive panel assembly. In an advantageous embodiment, diffuser 42 comprises a glass or translucent plastic sheet that also serves to seal or water-proof light fixture 10 at its front surface. This glass diffuser sheet 42 may be covered at its edges by bezel 20 and silicone potting material (not shown) may be used under the bezel to support the diffuser sheet 42.

The bezel 20 of the frame 12 comprises a front cover that covers the first edge channel 32 at the front surface of the light fixture 10. The front cover or bezel 20 has a width greater than or equal to the width of the first edge channel. The frame 12 includes a floor 46 disposed at its bottom (or rear). Floor 46 includes or supports a platform 48 for the reflective film 44 and the other components of optically transmissive panel assembly 26.

Driving circuitry, designated generally as 50, is disposed within the first edge channel 32 and operatively coupled to the set of LEDs 36. In a preferred embodiment, driving circuitry 50 is configured to convert an AC input into a DC output suitable for powering the LED panel, as generally disclosed in U.S. Patent Application No. 20120320627 A1, Flat Panel Lighting Device and Driving Circuitry. The driving circuitry 50 is operatively coupled to an AC power supply external to the light fixture 10 (not shown) to power the set of light emitting diodes (LEDs). Power may be provided by a cable or wire 51 provided access through an opening 53 in the floor 46 of the frame 12. Cable 51 may be connected to the external AC power supply through a wall outlet, junction box, or other form of electrical connection.

An adhesive thermal film such as adhesive tape 52 provides thermal and electrical isolation as well as spacing of the bottom of the driving circuitry relative to the floor 46 of the frame 12. Other strips of adhesive tape 54, 56 provide similar features. A metal enclosure 58 isolates driving circuitry 50. A second inner wall 60 extends from the platform 48. The second inner wall 60 supports the LEDs strip 36 and serves to dissipate the heat thereof. A second edge channel 62 is thus defined between the second edge wall and the second inner wall. The second edge channel 62 may be used to provide access to other components of the light fixture 10. Additional edge channels at other sides of light fixture 10 can be provided in a similar manner.

Referring now to FIGS. 5 and 6, alternative lighting fixture embodiments with additional edge channels are shown in schematic views. The lighting fixtures of FIGS. 5 and 6 include driving circuitry in multiple pieces (in FIG. 5—two pieces; in FIG. 6—three pieces) distributed across multiple edge channels of the LED panel lighting fixtures. These multiple-piece driving circuit layouts accommodate longer driving circuits, which may provide additional power and/or additional control functions. Dimensions (length, width and height) described above for driving circuitry in the first edge channel also are suitable for additional driving circuitry segments in additional edge channels.

FIG. 5 shows a lighting fixture 10′ including a frame 12′ with a first edge wall 28′ and a first inner wall 34′ defining a first edge channel 32′, a second edge wall 30′ and a second inner wall 60′ defining a second edge channel 62′, a third edge wall 66 and a third inner wall 68 defining a third edge channel 70. Lighting fixture 10′ has a rectangular form factor; other polygonal form factors are also possible (e.g. octagonal). The first edge channel 32′ may contain, for example, a first driving circuitry portion comprising an AC/DC transformer 72. The second edge channel 62′ may contain, for example, a LED array 40′, and the third edge channel 62′ may contain, for example, a second driving circuitry portion comprising a DC power supply 74. Thus, the frame can be configured to house or otherwise support LED power circuitry as well as associated wiring and electrical connections between the power circuitry and the LED arrays.

Referring to FIG. 6, an embodiment 10″ including a frame 12″ is illustrated, having a fourth edge channel 76 adjacent a fourth edge wall 78, so that a first edge channel 80 may contain, for example, an AD/DC transformer 82, a second edge channel 84 may contain, for example, a first portion 86 of a DC power supply, and the fourth edge channel 76 may contain, for example, a second segment 77 of a DC power supply. The second segment 77 of the DC power supply can be used for example to provide additional control functions such as dimming functions, and driving LEDs with multiple correlated color temperature control (CCT) values. Control functions also may include communications, such as audio or video signals. A third edge channel 88 may contain, for example, an LED array 90. As used herein, use of the ordinal numbers first, second, third, and fourth to designate the edge walls and channels is for the purposes of explanation and illustration; such designations not being for the purposes of limitation. As applied to different embodiments, different ordinal numbers may be used to refer to a corresponding side of the frame (e.g. the side containing an LED array).

FIG. 11 shows an advantageous embodiment of a first driving circuitry portion 72 comprising an AC/DC transformer, and a second driving circuitry portion 74 comprising a DC power supply, generally in accordance with FIG. 5. First driving circuitry portion 72 and second driving circuitry portion 74 are separate pieces in an L-shaped configuration, interconnected by wires or other electrical connectors. First driving circuitry portion 72 includes a printed circuit board substrate 130 with a metal heat sink backing (i.e. heat dissipating layer) 132. The circuit board substrate 130 and the metal heat sink backing 132 are oriented vertically in first edge channel 32′, and the metal heat sink backing is mounted against the first edge wall 28′ of frame 12. Similarly, second driving circuitry portion 74 includes a printed circuit board substrate 140 with a metal heat sink backing 142. The circuit board substrate 140 and the metal heat sink backing 142 are oriented vertically in second edge channel 62′, and the metal heat sink backing 142 is mounted against the second edge wall 30′ of frame 12. Metal heat sink backing 132 and metal heat sink backing 142 may comprise aluminum pieces of similar length and width to the dimensions of circuit board substrate 130 and printed circuit board substrate 140. These heat sink backing pieces may include slits (not shown) along their length in order to facilitate heat dissipation.

Various circuit components are mounted to the surface of circuit board substrate 130 facing the interior of first edge channel 32′, and various circuit components are mounted to the surface of circuit board substrate 140 facing the interior of second edge channel 62′. Advantageously, these circuit components are arrayed serially, e.g. single-file, along the length of the circuit board substrates, in order to reduce width of the circuit board substrates. Exemplary dimensions of these structures are a width in the range 12-18 mm, and thickness (including the heat sink pieces, printed circuit board, and components) in the range 12-14 mm.

The use of low-profile power supplies such as the multi-piece power supplies of FIGS. 5, 6 and 11 can improve the exterior design of LED panel lighting fixtures, for example in relatively small LED panel lighting fixtures. Referring to FIG. 3, by reducing the width of the first edge channel 32, it is possible accordingly to reduce the width of bezel 20 since the bezel should be as wide as or wider than the edge channel. Likewise, reducing the width of edge channels at other edges of the LED panel fixture 10 permits reduced width of bezel 20 at these edges as well. Typical bezel widths in LED panel lighting fixtures are on the order of 35-40 mm, which can be unsightly in relatively small lighting fixtures. In one example of an improved lighting fixture design based upon a low-profile power supply, an LED panel fixture 150 mm in length by 150 mm in width has a channel width of about 16 mm and a bezel width of 20 mm. In another example, an LED panel fixture 100 mm in length by 100 mm in width has a channel width of about 12 mm and a bezel width of 15 mm.

Turning now to FIG. 7, this view provides an enlarged sectional view of the portion of the light fixture 10 including the optically transmissive panel assembly 26. The light guide plate or LGP 27, is designed to receive light at an edge surface of LGP 27 from an array of light emitting diodes (LEDs), one of which is shown at 40 in this view along with lens 92. Light guide plate 27 redirects the light in a desired pattern to be projected from a front surface of the plate. The LGP may be comprised of an extremely transparent plastic material such as an acrylic or polycarbonate resin; e.g. LGP 27 may be made from poly(methyl methacrylate) (PMMA) resin. On the bottom of the light guide plate a matrix of lines or microstructures 94 can be formed. The microstructures at the bottom of the plate, or particulate additives, direct light received by the light guide plate out of the front of the plate.

One manufacturing technique molds or otherwise forms microstructure elements across a bottom face of the light guide plate. Geometrical and optical properties of microstructure elements can be changed independently, using parametric or non-parametric controls. Size, shape, depth, pitch, density, and angle of rotation of the microstructures all can be controlled to provide greater uniformity of brightness, or other output luminance distribution. For example, light extraction microstructures may be pyramidal, hemispherical, or semiellipsoid, among other forms.

In V-cutting, a V-shaped blade creates a grid on the bottom of the panel by etching a series of vertical and horizontal lines. The depth and spacing of these lines is chosen to optimize the evenness and brightness of light released from the panel. Commonly, in order to achieve uniform brightness, vertical V-grooves are widely spaced when they are close to the light source, but narrowly spaced when they are farther away from the light source. Horizontal V-grooves gradually grow wider and deeper as their distance from the light source increases. These V-groove arrangements provide markedly improved uniformity of brightness at the front surface of the LGP.

In printed-dot light guide plates, a matrix of fine dots is printed onto the LGP using diffusive ink. These dots help scatter the light emitted from the light source. Dot printing is a quicker and cheaper process than molded microstructures or V-cutting, but the printed ink dots are less effective at refracting light and therefore not as bright. Yet another method is to add particulates to the resin itself. These minute particles are scattered throughout the panel and reflect light in all directions when combined with a light source. Similarly to dot printing, the particulates do not reflect as much light out of the front of the panel as V-cutting or microstructures. Other techniques for forming light extraction structures in light guide plates include chemical-etching and laser-etching.

The light guide plate may include reflective surfaces (e.g. coatings) at other side surfaces besides the surface that receives light from the array of light emitting diodes (LEDs), to reflect light incident on these surfaces back into the light guide plate 27. As discussed above, and seen in FIG. 7, a reflective film or reflector 44 may be provided below the bottom surface of the light guide plate 27 to reflect light that is refracted out of the bottom surface back through the light guide plate 27.

The LED panel fixture may include light-transmissive sheeting or film that receives light from a front surface of the light guide plate and transmits light from the emission area of the light fixture. The light-transmissive sheeting or film can be rigid or flexible, and may include a single layer or multiple layers of translucent material. The light transmissive sheeting or film can include a diffuser, which scatters the light received from the light guide plate. Instead of or in addition to the diffuser, the light-transmissive sheeting or film can be configured to modify or otherwise direct the distribution of light received from the reflection panel in a variety of ways (herein called “patterning optics”). The light-transmissive sheeting or films embodiment of FIG. 7 includes both patterning optics 29 adjacent light guide plate 27, and diffuser sheet 42 comprising the outer (front) surface of the optically transmissive panel assembly 26. (As used in this patent application in referring to the patterning optics, the term “adjacent” the light guide plate includes the patterning optics being integral with the light guide plate).

The patterning optics 29 may comprise a prism film such as such as a brightness enhancement film (BEF), or a microprism array. Brightness enhancement films are transparent optical films that focus the light toward a viewing axis, providing a significant increase in brightness along this axis. Microprism arrays, i.e. sheets or films with grids of fine prisms, are well known in LED lighting applications. For example the use of microprism sheets in LED lighting systems is disclosed in U.S. Pat. No. 6,331,915, Lighting Element including Light Emitting Diodes, Microprism sheet, Reflector, and Diffusing agent.

Alternatively, the patterning optics 29 may comprise a micro-lens diffuser. In a patterning optics with micro-lens surface elements, the slope of the surface elements dictates the exit direction of a light ray. In a micro-lens diffuser film, light-steering elements called micro-lenses typically cover the entire exit side. Micro-lens arrays are known to produce uniform scatter patterns with high efficiency. Two key factors affecting luminance of light exiting the micro-lenses is the contour of the micro-lenses, and the pitch between micro-lenses.

A range of patterning optics products is available under the trademark Light Shaping Diffusers (LSD)® from Luminit, LLC, Torrance Calif. Light Shaping Diffusers work on a principle of multi-stage optics in which firstly, the light is collimated to a narrow angle, and then the light is shaped to a desired output angle that can vary from very narrow to wide with no change except for the light shaping diffuser. Secondary optics acting on the LEDs output, such as light guide plates in combination with a brightness enhancing film, are used to narrow and collimate the beam. The Light Shaping Diffusers then acts as tertiary optics to shape the output beam. For example, after an initial stage of collimating the beam angle to 5°, Luminit's LSD® materials can provide a very narrow output of 7° with a 5° diffuser up to 80° with an 80° diffuser. These Light Shaping Diffusers also can shape the beam output from circular to highly elliptical.

Patterning optics materials also are available from Fusion Optix Inc., Woburn Mass., under the trademark AirOptics. AirOptics™ films and sheeting include a variety of microlens films and prism films, as well as diffusers and reflecting films, for LED lighting applications. Patterning optics materials from Fusion Optix can be included in the LED panel lighting fixtures of the present invention to provide various patterned luminous intensity distributions described below, including asymmetric light distributions, elliptical light distributions, and narrowed beam angles.

In the embodiment of FIG. 7, the light guide plate 27 receives light from a LED light source 40 including LEDs 36. Light guide plate 27 includes a plurality of microstructures 94 disposed on its bottom surface. Light beams emitted from LEDs 36 enter the light guide plate 27 at the edge surface 38 of the LGP. Then, by means of the microstructures 94 which disrupt the total internal reflection, a portion of the light beams is reflected upward to leave the light guide plate 27 from the front surface of the light guide plate 27. The remaining portion of the light beams leaves the light guide plate from the back surface of the light guide plate, and is reflected upwardly by the reflector 44 to enter into the light guide plate 27 again, and then exit the LGP 27 from its front surface. An illumination angle(s) of light emerging from the LGP front surface is adjusted by the patterning optics 29. The patterning optics 29 and/or the LGP microstructures 27 may be designed to provide a desired luminous intensity distribution of light projected by the LED panel fixture, such as a patterned luminous intensity distribution.

As used in the present patent application, the phrase “patterned luminous intensity distribution” refers to a light output from the LED panel light fixture of the present invention that departs from the luminous intensity observed from an ideal diffuse radiator (sometimes called Lambertian radiance), and that often is tailored to the lighting requirements of particular applications. Examples of patterned luminous intensity distribution include (but are not limited to) the following luminous intensity distributions of an LED panel lighting fixture:

(a) Asymmetric Light Distributions

LED panel fixtures providing asymmetric light distribution at a transverse direction toward one side of light fixture, which directs the light with maximum luminous intensity at an angle toward that side of the light fixture. For example, in the light fixture 10 of FIG. 1, an asymmetric light distribution may provide maximum luminosity at an acute angle from normal 64 emitted from the light fixture generally in the transverse direction A (although not necessarily in that precise direction). As defined in this patent application, asymmetric light distributions do not provide off-normal maximum luminosity at both sides of the light fixture.

FIG. 14 is a polar graph of candlepower distribution for an exemplary asymmetric light distribution. Referring to FIG. 1, this graph indicates luminous intensity in all vertical angles of the LED panel light fixture measured in a plane including the normal 64 and one of the axes A and B; vertical angle 90° corresponds to normal 64.

Various applications using asymmetric light distributions are discussed below. For example, in the under cabinet LED panel light of FIG. 8, the lighting fixtures 105, 110 are located toward the back edge of a countertop 97, and provides a luminous intensity distribution that has a maximum luminous intensity angled toward the center of the countertop (grid 100) rather than at a normal from the light fixture's emission area.

In another asymmetric lighting application, LED panel lighting fixtures are wall mounted adjacent the edges of an object, such as light fixtures 104, 106 adjacent the vanity mirror 108 of FIG. 9. These lighting fixtures provide a light output to one side of each lighting fixture to direct the light with maximum luminous intensity toward a location in front of the object, such as a viewer in front of the vanity at the center of the mirror.

In further asymmetric lighting applications, vertical or horizontal surfaces can be “washed” with light, with the highest intensity light aimed near a portion of the washed surface offset from a normal to the LED panel lighting fixture. One such application is the wall wash lighting system 150 shown in the schematic view of FIG. 12. Light fixture 151 (here viewed at one of its short edges) is mounted on ceiling 156, and emits light 154 angled downward in a transverse direction to illuminate painting 152 or other object mounted on wall 158. Another such application is the step lighting system 160 shown in the schematic view of FIG. 13. Light fixture 161 (here viewed at one of its short edges) is mounted on wall 166, and emits light 164 angled downward in a transverse direction to wash step 162 or other walkway with light.

(b) Light Distributions with Major and Minor Beam Widths

Beam angle (also sometimes called beam diameter or beam width) is the degree of width that light emanates from a light source. In lighting, beam angle is the angle between those points on opposite sides of the beam axis where the intensity drops to 50% of maximum, sometimes called full width at half maximum (FWHM). The term beam diameter usually refers to the beam width of a beam of circular cross section, but may also refer to a beam of elliptical cross section. As further described below with reference to FIG. 8, the light fixture of the invention may provide an elliptical luminous intensity distribution in which the major axis extends along a longitudinal direction, and the minor axis extends along a transverse direction. An elliptical luminous intensity distribution has a different diffusion angle (i.e. exit angle of collimated light through a material) for light exiting the emission area 18 in the longitudinal direction, than for light exiting the emission area 18 in the transverse direction (FIG. 1).

(c) Light Distributions with Narrow Beam Angles

Another type of patterned luminous intensity distribution that may be achieved using patterning optics in the LED panel light fixtures of the present invention is narrow beam angles, which are sometimes achieved in other types of lamps or luminaires through the use of reflector systems. Lamp type terms such as “spot” and “flood” have been adapted to LED lamps. For example, ENERGY STAR® Program Requirements for Integral LED Lamps provide that for LED lamps falling within the guidelines, suppliers are required to state the beam distribution in terms of Spot, Narrow Flood, or Flood, based upon the following definitions: “Spot” for 10°-20° beam angle; “Narrow flood” for 20°-30° beam angle; and “Flood” for greater than 30° beam angle.

FIG. 15 is a polar graph of candlepower distribution for a 25° narrow light distribution. Referring to FIG. 1, this graph indicates luminous intensity in all vertical angles of the LED panel light fixture measured in a plane including the normal 64 and one of the axes A and B; vertical angle 90° corresponds to normal 64.

(d) Glare Control

Yet another way in which the LED panel lighting fixtures of the invention can control luminous intensity distribution is to limit glare. Glare can be categorized into different visual effects, for example blinding glare, disability glare, and discomfort glare. LED panel lighting fixtures 10 can avoid or reduce unwanted levels of glare by diffusing the fixtures' light output and by redirecting light away from the viewer.

Referring now to FIG. 8, an application of the present invention in an under cabinet lighting installation is designated generally as 96. This installation includes LED panel lighting fixtures 105, 110 facing downwardly over countertop 97 and mounted in a spaced apart configuration under a cabinet in the vicinity of a back wall or backsplash 101. Installation 96 is characterized by a length axis L along the countertop, width axis W across the countertop, and height axis H above the countertop. With reference to these coordinates, the LED panel lighting fixtures 105, 110 are separated by L₁ (center-to-center spacing), countertop 97 has a width W₁ from the backsplash to its front edge, and lighting fixtures 105, 110 are placed at height H₁ above countertop 97 as measured at the front surface (emission area) of these lighting fixtures.

Light outputs of the LED panel lighting fixtures as received at the countertop 97 and backsplash 101 can be quantified using photometry, by illuminance or the total luminous flux incident on these surfaces per unit area. Dotted grids 98, 100 respectively overlaid at the backsplash and at the countertop schematically illustrate areas (rectangular zones) of these two surfaces at which light is received from lighting fixtures 105, 110.

Advantageously, lighting fixtures 105 and 110 each provide light output with patterned luminous intensity distribution. In a first embodiment, fixtures 105 and 110 provide a substantially elliptical illuminance pattern at countertop 97 with major and minor beam widths beam widths, as measured respectively along the length axis L (longitudinal direction of the light fixtures) and width axis W (transverse direction of the light fixtures). Further, fixtures 105 and 110 provide an overlapping luminous intensity distribution so that in zones within grid 100 that receive overlapping illumination from the two fixtures, the total illuminance includes significant light output contributions from both lighting fixtures. The overall effect of the physical layout and light outputs of lighting fixtures 105 and 110 is that these fixtures provide a more uniform light distribution along countertop 97.

In a second embodiment of patterned luminous intensity distribution for under cabinet light installation 96, LED lighting fixtures 105 and 110 are mounted near the back wall 101. A normal from the emission area, or nadir (e.g. see also numeral designation 64 in FIG. 1), extends downwardly along axis H and intersects the grid 98 near the back edge of the grid. In order to provide more uniform illuminance across the width of countertop 97, and to limit illuminance at the backsplash (grid 98), light fixtures 105 and 110 provide an asymmetric luminous intensity distribution with maximum luminous intensity in a transverse direction near the middle of grid 100 rather than at the nadir near the back edge of the grid 100. This second embodiment of patterned luminous intensity distribution may be combined with the first embodiment of patterned luminous intensity distribution for an under cabinet LED panel lighting system.

Referring now to FIG. 9, utilization of the present invention with a vanity mirror is illustrated, designated generally as 102. Two LED panel fixtures 104, 106 are shown mounted adjacent left and right edges of a vanity mirror 108. Each of the LED panel fixtures 104, 106 provides a luminous intensity distribution skewed in a transverse direction toward the side of that lighting fixture that faces the vanity mirror 108. The luminaire angle(s) of maximum luminous intensity for each lighting fixture is directed toward a location centered in front of the mirror 108, rather than to a location in front of the respective lighting fixture. This off-normal luminous intensity distribution reduces glare for persons in the general vicinity of the LED panel lighting fixtures 104, 106.

Turning now to FIG. 10, another aspect of the disclosed technology will be described. Color of a white lamp can vary from yellowish, to neutral white, to bluish; the correlated color temperature (or “CCT”) rating of a lighting fixture is a general measure of its “warmth” or “coolness” of appearance. In accordance with one exemplary embodiment, the LED panel light fixture can include multiple sets of LEDs, wherein each set corresponds to a given correlated color temperature. For example, the light fixture can include a first set of LEDs 120 a with a first CCT, and a second set of LEDs 120 b with a second CCT, along with driving circuitry operatively coupled to the first set of LEDs 120 a and the second set of LEDs 120 b. The first driver and second driver may be located, for example, in the driver circuitry shown at 76 in FIG. 6, or other suitable location.

Referring again to FIG. 8, in an under cabinet lighting installation, appropriate light color depends on the surface(s) of countertop 97 to be illuminated. For wood tones, wood-colored tiles, copper-tones, or warm-toned surfaces, it is desirable to have a light with correlated color temperatures (CCTs) in the 2700-3500 K range (warm tone). For glass tiles, CCTs in the 3500-5000K range are appropriate (neutral or cool tone). For a countertop 97 having multiple surface materials along the axis L, color control can be achieved by providing multiple zones of illumination of various CCT's, depending on the nature of the countertop surface in each zone.

To illustrate aspects of the disclosed technology in a clear and concise manner, the drawings may not necessarily be to scale and certain features may be shown in somewhat schematic form.

Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application. 

1. A light fixture, comprising: a) a frame having a frame length measured along a length axis and a frame width measured along a width axis, wherein the frame length is greater than the frame width; b) an optically transmissive panel assembly disposed within the frame; c) a set of light emitting diodes (LEDs) extending along the length axis adjacent an edge surface of the optically transmissive panel assembly; and d) driving circuitry disposed within the frame and operatively coupled to the set of LEDs, the driving circuitry operatively coupled to a power supply external to the light fixture to power the set of light emitting diodes (LEDs); wherein the optically transmissive panel assembly receives light from the set of light emitting diodes (LEDs) and emits light in a patterned luminous intensity distribution.
 2. The light fixture of claim 1, wherein the optically transmissive panel assembly comprises a light guide plate.
 3. The light fixture of claim 2, wherein the optically transmissive panel assembly further includes a patterning optics adjacent the light guide plate.
 4. The light fixture of claim 3, wherein the patterning optics comprises a micro-prism film.
 5. The light fixture of claim 3, wherein the patterning optics comprises a micro-lens diffuser film.
 6. The light fixture of claim 1, wherein the optically transmissive panel assembly emits light in an asymmetric light distribution.
 7. The light fixture of claim 6, wherein the asymmetric light distribution provides maximum luminosity in a transverse direction from the light fixture.
 8. The light fixture of claim 1, wherein the optically transmissive panel assembly emits light in a light distribution with narrowed beam angle.
 9. The light fixture of claim 1, for illuminating an elongate surface, wherein the optically transmissive panel assembly has a diffusion angle for light emitted in a longitudinal direction, that is different than a diffusion angle for light emitted in a transverse direction.
 10. The light fixture of claim 1, wherein the optically transmissive panel assembly emits light in an asymmetric light distribution with highest intensity light aimed at a surface offset from a normal to the light fixture.
 11. The light fixture of claim 6, wherein the light fixture is located adjacent an edge of an object, and the optically transmissive panel assembly emits light with maximum luminous intensity at an angle toward a location in front of the object.
 12. A light fixture, comprising: a) a frame including a first edge wall and a second edge wall, wherein a first edge channel is defined within said frame adjacent said first edge wall and a second edge channel is defined within said frame adjacent said second edge wall; b) a set of light emitting diodes (LEDs) disposed within the frame; c) driving circuitry disposed within said first edge channel and operatively coupled to the set of LEDs, the driving circuitry operatively coupled to a power supply external to the light fixture to power the set of light emitting diodes (LEDs), said driving circuitry comprising a first circuitry segment disposed within said first edge channel and a second circuitry segment disposed within said second edge channel and in electrical communication with said first circuitry segment.
 13. The light fixture of claim 12, wherein the frame is substantially rectangular in form, the first edge channel extends along a length axis, and the second edge channel extends along a width axis.
 14. The light fixture of claim 12, wherein the frame has a thickness of 18 mm or less.
 15. The light fixture of claim 12, wherein the first circuitry segment disposed within the first edge channel has a length and a width, wherein a length-to-width ratio thereof is at least 10 to
 1. 16. The light fixture of claim 12, wherein the first circuitry segment and the second circuitry segment each comprises a printed circuit board, with components arrayed serially along a length of the printed circuit board.
 17. The light fixture of claim 15, wherein the first circuitry segment comprises a printed circuit board oriented vertically within the first edge channel.
 18. The light fixture of claim 16, wherein the first circuitry segment is mounted to the first edge wall with a heat dissipating layer between the printed circuit board and first edge wall.
 19. The light fixture of claim 12, wherein the frame includes: a third edge wall, a third edge channel is defined adjacent to said third edge wall, wherein the driving circuitry further comprises a third circuitry segment disposed within said third edge channel and in electrical communication with said second circuitry segment.
 20. The light fixture of claim 12, further comprising an optically transmissive panel assembly disposed within the frame, said optically transmissive panel assembly comprising a light guide plate, wherein the set of light emitting diodes (LEDs) are disposed adjacent an edge surface of the light guide plate. 